Why Brake-By-Wire Is Coming To Your Car

When a Formula 1 racing driver hits the brakes, he isn’t applying actual pressure to the master cylinder controlling the rear brakes. Instead, he’s sending a signal for the computer to interpret, and it’s the computer that determines how much pressure to apply to the rear brake calipers.

We call this technology brake-by-wire, because it cuts the physical link between the pedal and the brake system itself. (Throttle-by-wire and steer-by-wire exist as well.) Sensors and actuators read the amount of pressure a driver inputs, and this force is transferred to all the brakes from the master cylinder using hydraulic fluid.

Formula 1 has used the tech since 2014 for the rear brakes (the fronts are still conventional). Luxury carmakers have been experimenting with it. Soon, brake-by-wire might be making its way to your car.

Wire Is Better

Alfa Romeo

Toyota has been implementing brake-by-wire on hybrid (and a few non-hybrid) vehicles in its Lexus brand for years now. The newest player is Alfa Romeo, which is getting into the game with its Giulia and Stelvio.

Alfa’s unit was developed by Continental, better known for making tires. It’s a control module that runs more systems than just your basic brake actuation. It replaces the original brake booster, and it runs electronic stability control and ABS as well. These systems are traditionally run by separate modules, increasing complexity and weight in a car.

Brake-by-wire systems also stop sooner—and not just because the computer is faster than you. Alfa uses a massive brake booster that builds up pressure faster than a conventional booster does. This large brake booster gets used because it not only has to provide pressure to the master cylinder, but also to the brake pedal itself in an attempt to replicate pedal feel. A conventional braking system can go from zero braking force to full lock in 300 milliseconds, while Alfa’s IBS can accomplish the feat in 100 milliseconds thanks to the brake booster. This translates into shorter stopping distances in an emergency brake application.

Alfa Romeo Giulia Quadrifoglio brakes.

Alfa Romeo

Another huge benefit is the ability to customize pedal feel. Lots of cars now come with performance modes that automatically tweak the suspension settings at the push of a button. Brake-by-wire can do that for stopping power. In Race mode, the Giulia Quadrifoglio has a much stiffer pedal feel.

And carmakers have another rationale for embracing brake-by-wire. Alfa spokesman Berj Alexanian says, “The main reason for the choice to use a brake-by-wire system was that the Giorgio platform [which the Giulia and Stelvio are built on] was developed from a blank sheet, so the architecture has to be ready for additional powertrains beyond traditional combustion engines, which brake-by-wire will work well for down the road.”

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Reading in-between the lines here tells us to think electric, because hybrids and fully-electric vehicles use regenerative braking. This means that when you take your foot off the accelerator, the car uses the vehicle’s momentum as the mechanical energy to put the electric motor into reverse which generates electricity to recharge the batteries while slowing down.

Alfa, like many other manufacturers, will want to use an electrically controlled braking system to pair with the regenerative brakes. A mechanical system in the middle of all the electronics doesn’t allow for as much control over how the vehicle reacts to slowing down through the combination use of both regenerative braking and standard friction brakes. More control over the brakes means maximum power regeneration and a more seamless stop.

Coming Your Way?

Featuring brake-by-wire on a performance car like Alfa's is important because such vehicles are a test bed to see how enthusiasts react to electric systems replacing mechanical counterparts. Steer-by-wire offered on the Infiniti Q50 has long been criticized for having steering feel akin to a video game wheel, while the general reception to Alfa’s Integrated Brake System (IBS) has been nothing but positive.

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Simulating brake feel is a separate challenge. Driving a car with a fully hydraulic brake system, for example, you can physically feel the pedal becoming softer as it heats up or overheats the brakes. If all you’re pressing on is a wire that sends a signal to a control unit, then that physical sensation linked to overheating brakes is gone. It’s up to the computer to do something about it.

In the Quadrifoglio’s case, a warning light on the dash tells you to settle down before you get yourself in real trouble. Berj says this braking feel is the only thing Alfa has tweaked since the initial release of the Giulia, and it did so by software update.

Alfa Romeo

Resistance and fear from drivers has been the major stumbling block to the creep of by-wire technologies into consumer cars. But they’re coming. Look at aviation, where an electronic interface called fly-by-wire endured the protests of traditionalists and eventually replaced most manual flight controls.

Brakes are still the most vital safety component on a car, so relying on an electric signal to make them function doesn’t necessarily instill trust in buyers. Thankfully, there are traditional hydraulic backup systems for all the brake-by-wire systems offered today. If the electrics ever went haywire, you shouldn’t ever find yourself traveling 70 mph down the highway without brakes in a car equipped with brake by wire.

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